<!DOCTYPE html>
<html>
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style>
		.red {
			background-color: red;
		}
	</style>
	<script src="../lib/zepto.min.js"></script>
	<script>
		$(document).ready(function() {
			// $('.test').css('background', 'red');
			$('.test').on('click', function() {
				var $this = $(this);
				$this.addClass('red');
			})
		});
	</script>
</head>
<body>

	<div class="test">
		test div
	</div>
	
</body>
</html>